1. Field of the Invention
The present invention relates in general to circuits for controlling a multiple of latching relays; in particular the present invention relates to a method and device design for controlling a multiple of latching relays which may be used as computer controlled switches.
2. Description of Related Art
Latching relays are well known in the art, and methods for controlling a single latching relay, or a few latching relays are also known. Prior art methods of controlling a single latching relay have included using one of a pair of power supplies for momentarily coupling the coil of a latching relay to set or reset the relay, depending on the power supply to which it was coupled. To use methods involving a pair of power supplies for each relay often also involves using a pair of switching devices for each relay. To control a multiple of latching relays with the known dual power supply methods often requires a duplication of most control components for each relay. The result would be a very expensive and complicated device with many components.
More sophisticated devices also exist in the prior art to control a multiple of latching relays, such as the device invented by Dalphee et al, disclosed in U.S. Pat. No. 4,040,119. In the Dalphee device a computer sends a control signal to a first monostable multivibrator which enables output driving devices that provide an operating current and voltage to latch each relay in a first position. The first monostable multivibrator then triggers a second monostable multivibrator which operates in conjunction with logic means to enable output driving devices that provide an operating voltage and current to latch selected relays in a second position. The Dalphee device therefore requires, for each relay to be controlled, a separate control line, a separate output driving device to provide operating current and voltage, and a large number of control components.
The known methods in the art to control a multiple of latching relays, in general, rely on at least one separate output driving device to provide operating current and voltage for each relay, and one separate control line for each relay. It is therefore not a simple matter to add or remove relays from the system, as a large number of components are involved when adding or removing even a single relay. A further draw back is that each time new relays are added, a new control line has to be added to the relay and also to the controlling computer or other controlling means. Therefore, if you wanted to control, for example, 900 relays, 900 control lines and 900 output driving devices would be needed. To add a further 50 relays, the controlling computer, or other controlling means, would have to be physically opened to add 50 additional control lines, and 50 additional control lines would have to be run to the 50 additional driving devices for the 50 additional relays.
A further draw back to many of the known methods of controlling a multiple of latching relays, is that to change the state of any one or any number of relays, all relays in the system have to be momentarily reset, and then those that are to be set would be immediately thereafter set.